Abstract： Since the concept of mixed connective tissue disease was proposed，it remains controversial in its pathogenesis and diagnosis.Mixed connective tissue disease is generally recognized as a disease entity characterized by overlapping clinical features of systemic lupus erythematosus，systemic sclerosis，and polymyositis，as well as high titers of serum anti-U1 ribonucleoprotein antibody.Studies have shown that up to 1/4 of the patients have the disease at an early age，with the first symptoms of Raynaud's phenomenon and polyarthritis，and the disease has certain differences in clinical characteristics and diagnosis and treatment from adults.The disease may evolve into other connective tissue diseases in the later stage，so early diagnosis and treatment are of great significance to improve prognosis.This article elaborates on the epidemiology，pathogenesis，clinical manifestations，diagnosis and treatment of juvenile mixed connective tissue disease.